Driving arrangement for initiating and controlling rotary movements of two driven components together with and relative to each other



March 21, 1961 H. F. BOVENSIEPEN 2,975,563

DRIVING ARRANGEMENT FOR INITIATING AND CONTROLLING ROTARY MOVEMENTS OF TWO DRIvEN COMPONENTS TOGETHER WITH AND RELATIVE TO EACH OTHER Filed April 11, 1960 2 Sheets-Sheet 1 Fly.

March 21, 1961 H. F. BOVENSIEPEN 2,975,563

DRIvING ARRANGEMENT FOR INITIATING AND CONTROLLING ROTARY MOVEMENTS OF Two DRIvEN COMPONENTS TOGETHER WITH AND RELA IVE To EACH OTHER Filed April 11, 1960 2 Sheets-Sheet 2 F/g N I? 5 x7 /9 /9 N 1? was 'yzs I E Z2 22 L J 62 E J gg ME a I 74 2/ K3 QM W WW HANS FRIEDRICH BOVENSI'PZ-N A: nrramey DRIVING ARRANGEMENT FOR INITIATING AND CONTROLLING ROTARY MOVEMENTS OF TWO DRIVEN CQMPONENTS TOGETHER WITH AND RELATIVE TO EACH OTHER Hans Friedrich Bovensiepen, Hasselerstrasse 32,. Methmann, Rhineiand, Germany Filed Apr. 11, 1960, Ser. No. 21,249

11 Claims. (Cl. 51--111) The present invention relates to improvements in a driving arrangement of the type adapted to initiate and control rotary movements of two driven components together with and relative to each other, in particular in the driving arrangement in a two-lap lapping or grinding machine for controlling the rotary movements of both lapping or grinding members.

In a two-lap lapping or grinding machine, the lapping or grinding discs (hereinafter referred to as lapping members or laps) are normally rotated in opposing directions; for example, the lower lapping member is continuously driven in clockwise direction and the upper lapping member is rotated in anticlockwise direction. However, it is frequently necessary to rotate the upper lapping member in the same direction as and at the exact speed of the lower lapping member; to disconnect the upper lapping member from its drive while permitting it to rotate freely with the lower lapping member, i.e. merely under the action of frictional forces generated between its lapping surface and the workpieces; or to positively arrest the upper lapping member. Heretofore, such movements were carried out by lapping members each of which was driven by a separate motor. Of course, the provision of two separate motors always increases the initial cost of the lapping machine and results in higher power consumption as well as in higher expenditures for maintenance and repair work. In addition, when the lapping members rotate in the same direction, care must be taken that their angular speeds remain identical, i.e. that no angular movements of one lapping member with respect to the other lapping member will take place. This is particularly important when the lapping machine is utilized in the treatment of comparatively small workpieces since the latter would tend to tilt in response to extremely small differences in the angular speed of the lapping members which would result in improper finish of their farm, i.e. the faces of the workpieces treated by the lapping surfaces of the lapping members would be out of exact parallelism with each other.

In order to avoid the drawbacks of twin-motor, twolap lapping machines, it was already proposed to rigidly connect the lapping members with each other by means of a spindle which is coaxially fixed to the hub of each lapping member. However, the spindle then occupies such space which is necessary for other purposes and, even more important, the spindle complicates the construction of the lifting assembly which is normally provided in a two-lap lapping machine for moving the upper lapping member toward and away from the lower lapping member.

An important object of the present invention is to provide a driving arrangement which is capable of driving two driven components, e.g. the lapping members of a two-lap lapping machine, in such a way that the components are rotatable together with and with respect to each other and that one of the components is either free to rotate with or is positively arrested against movements 2,975,563 ?atented Mar. 21, 1961- with respect to the other driven component, and which is capable of performing the just outlined functions without requiring a direct connection between the driven components.

Another important object of the present invention is to provide a driving arrangement of the above outlined characteristics which is of very simple construction; which occupies very little space in a two-lap lapping, grinding or like machine; and which comprises a sma number of readily accessible component parts.

A further important object of the invention is to provide a driving arrangement of the above outlined type which utilizes a single driving motor for initiating the rotary movements of both driven components.

A concomitant object of the instant invention is to provide a drivin arrangement for initiating and controlling rotary movements of two lapping members in a two-lap lapping machine together with and relative to each other which is constructed and assembled in such a way that it requires only small changes in the design of such machines and which, therefore, may be readily incorporated in lappin machines of presently known construction.

With the above objects in View, the invention resides essentially in the provision of a driving arrangement which comprises a first and a second driven member, eg the driving pulleys for the upper and lower lapping members of a two-lap lapping machine; a pair of driven gears coaxial with each other and with at least one of the driven members, one of the gears being drivingly connected to the other driven member; an assembly including a single driving motor for rotating the gears in opposing directions; and a coupling member which is axially shiftable with respect to the gears and which is drivingly connected with the one driven member and is alternately connectable with the gears to rotate the last mentioned driven member in clockwise or counterclockwise direction. The coupling member has a neutral axial position in which it is disconnected from the gears whereby the dliven member connected therewith is free to rotate with respect to the gears and with respect to the other driven member. The arrangement may comprise a stationary braking member which may be connected with the coupling member when the latter is disengaged from the gears in order to hold that driven member which is connected therewith against rotary movements. The braking member may constitute a portion of the center support which mounts the upper frame of a two-lzap lapping machine, and the means for drivingly connecting the driven gears with the single motor preferably comprises a pair of driving gears the first of which is in direct mesh with one of the driven gears and the second of which rotates the other driven gear by means of an intermediate gear so that the two driven gears rotate in opposing directions.

The means for alternately connecting the coupling member with the driven gears and with the braking mem-. ber may comprise suitable clutch members mounted on the coupling member, on the braking member and on each gear. For example, the clutch members on the coupling member may comprise several groups of annularly arranged, axially parallel splines or keys, while the clutch members of the gears and of the braking member then comprise grooved portions surrounding the axial, bores of the respective parts to receive and to engagewill be best understood from the following detailed description of a specific embodiment when read in connection with the accompanying drawings, in which:

Fig. 1 is a schematic side elevational view of a two-lap lapping machine embodying my invention, certain portions, of the upper and lower frames being broken away to reveal the driving arrangement; and

Fig. 2 is a schematic side elevational view, drawn to a greatly enlarged scale, of the shiftable coupling memher in five different positions.

Referring .now in greater detail to the drawings, and first to Fig. 1, there is shown a two-lap lapping or grinding machine LM which comprises a lower frame or base 1 mounting'the vertical shaft 2a of the lower lapping member or lap 2. The shaft 2a is rotated by a driven pulley 4a which is mounted at its lower end, this pulley receiving rotation from a lower driving pulley 4 through an endless belt 3. The vertical shaft 4b of the driving pulley 4 is mounted in the member 33 forming part of the frame 1 and is rigidly connected with a driven spur gear 12 which latter is in permanent mesh with a driving spur gear 9 mounted on and keyed to a vertical shaft 31 which is installed in the lower frame or base 1. The shaft 31 carries a worm wheel 6a which meshes with a worm 6, the latter being rotated by a driven pulley 7a. The pulley 7a is driven by an endless belt 7 which receives motion from a driving pulley 7b fixed to the shaft of an electric motor 8 mounted in the lower frame 1.

Adjacent to the lower lap 2, the lower frame 1 is formed with an upwardly extending center support or column 14 which rotatably supports the upper frame 13. This latter frame mounts the upper lapping member or lap 15 which is fixed to the lower end of a vertical driving shaft 15a. The shaft 15a is mounted in and is vertically reciprocable by a spindle sleeve 23 in a man ner which forms no part of the present invention. The non-represented upper end of the driving shaft 15:: is driven by an endless belt 16 which receives motion from an upper driving pulley 17 mounted above the center support 14. The upper frame 13 comprises a shell 28 which coaxially surrounds the center support 14 and is mounted in a ball bearing 29 and a needle bearing 30. The ball bearing 29 takes up the weight of the upper frame 13 and the upper radial forces acting between the parts 14 and 28. The open upper end of the shell 28 is covered by a flanged collar 27 which receives two sets of ballbearings 26 mounted externally of a hub 25 forming part of the upper driving pulley 17. By swinging the upper frame 13 about the common axis of parts 14, 28, the upper lap 15 may be moved into and out of vertical alignment with the lower lap 2. When in the aligned position of Fig. 1, the adjacent lapping surfaces 2, 15' may act upon a series of schematically represented workpieces 24 to perform a smoothing, grinding or lapping operation whose exact nature depends upon the composition of the lapping surfaces 2 and 15.

The invention resides in the provision of a driving arrangement which is adapted to connect the driving pulley 17 for the upper lap for rotation with the driving pulley 4 of the lower lap 2, to rotate the upper pulley 1'7 and the upper lap 15 in a direction counter to that in which the lower lap 2 is driven, to arrest the upper driving pulley and the upper lap while the lower lap 2 continues its rotarymotion, or to permit the upper lap 15 to continue its rotary motion merely by frictional engagement of its surface 15 with the workpieces 24. The driving arrangement 5 comprises the aforementioned electric motor 8; the means 7, 7a, 7b, 6, 6a and 31 for rotating the driving spur gear 9 and a second driving spur gear 10 which latter is also mounted on and keyed to the shaft 31; the driven spur gear 12; a coaxial second driven spur gear 11 which latter is rotatably mounted at the lower end of a stub shaft assembly 32 fixed to the frame 1; an intermediategear 34 which is in permanent mesh with the gears 10, 11 and whose shaft 34a is mounted in the frame 1; and a vertically shiftable, elongated, rod-shaped coupling member 18 which is rotatably mounted in the lower frame 1, whose upper end extends into the hollow hub of the upper driving pulley 17, and whose lower end extends coaxially through the driven gear 11 and is projectable all the way into the coaxial bore of the lower driven gear 12. It will be seen that the driving pulleys 4, 17', constituting the driven members of the driving arrangement 5, and the driven gears 11, 12 are coaxially aligned with each other, with the vertically shiftable coupling member 18, and with the -parts 14, 28. Owing to provision of the intermediate gear 34, the upper'driven gear 11 rotates in a direction counter to that of the lower driven gear 12. The means for axially shifting the coupling member 18 in the directions indicated by the double arrow 35 is not shown in the drawings. For example, the member 18 may be shifted by hand, by means of a suitable linkage or in a fully automatic way.

Fig. 2 illustrates five different axial positions of the shiftable coupling member 18. This member comprises an external annular portion 21 constituting a clutch memher and consisting of a series of uniformly spaced, radially arranged, axially parallel splines or keys which are located close to its lower end, and two similarly formed annular portions or clutch members consisting of splines 19, 29 both adjacent to the upper end of the member 18. The coaxial bores of driven gears 11, 12 are bounded by clutch members consisting of gear portions formed with axially parallel grooves 11a, 12a, respectively, or such configuration as to receive the splines 21 when the coupling member 18 is moved from the position N into the positions L, R, respectively. The upper end of the center support 14 comprises a horizontal discoid portion 22 which constitutes a braking member and is formed with a coaxial bore bounded by a clutch member having axially parallel grooves 22a adapted to receive the splines 20, and similar axially parallel grooves 25a are provided in the hub 25 of the upper driving pulley 17 for reception of the splines 19. The length of the hub 25 is such that the splines 19 constantly connect the pulley 17 with the axially reciprocable coupling member 18 regardless of the latters momentary axial position, i.e. any rotary or braking action imparted to the coupling member 18 is immediately transmitted to the upper lap 15.

As is shown in the left-hand part of Fig. 2, the coupling member 18 assumes its neutral position N when the splines 20 are out of mesh with the fixed braking member 22 and the splines 21 do not engage with the driven spur gears 11, 12. Thus, while the gear 12 continuously rotates the lower lap 2 through the pulleys 4, 4a, the belt 3 and the shaft 2a, the upper lap 15 is disconnected from the gears 11, 12 of the driving arrangement 5 and merely trails the rotary movements of the lower lap 2 by virtue of its own weight and of the frictional force existing between the lapping surface 15 and the rotating workpieces 24.

When the coupling member 18 is shifted downwardly into the position R, its splines 21 enter the grooves 12a in the lower driven gear 12 whereby its splines 19 transmit rotation to the upper driving pulley 17, i.e. the laps 2 and 15 then rotate in the same direction, e.g. clockwise engages only with the hub. 25 of the upper driving pulley 17 but is not driven by the gear 11 or 12. Thus, this position substantially corresponds to the position N with the exception that not only the splines 19 but the splines 20 also enter the grooved bore 25a of the hub 25.

By moving the coupling member 18 into its uppermos-t position L, the splines 21 enter the grooves 11a of the upper driven gear 11 and thus positively connect the upper pulley 17 with the driving motor 8 in such a Way that the laps 2, rotate in opposing directions.

An important advantage of the just described arrangement is in that the coupling member 18, when in the position R, positively prevents any angular displacements of the laps 2, 15 with respect to each other; such displacements could adversely aifect the lapping operation since the workpieces 24 would tend to pivot and could not be finished with a requisite degree of precision. This same coupling member 18 also brings about rotation of the laps 2, 15 in opposing directions and enables the upper lap either to follow the rotary movements of the lower lap 2 solely under the action of frictional forces, or to be arrested against rotation while the lower lap rotates.

Since the lapping machine utilizes a single driving motor 8 for both lapping members which is located in the lower frame 1, the weight of the upper frame 13 is reduced considerably; this is a decided advantage which is particularly felt when the upper frame must be swung about the common axis of driven members i, 17 and center support 14 to move the upper lap 15 into or out of vertical alignment with the lower lap.

It will be readily understood that the splines 19-21 and the complementary portions having grooves lia, 12a, 22a and 25a may be replaced by different types of clutch members as long as they enable the coupling rod 18 to assume the axial positions indicated in Fig. 2 for drivingly connecting the driven gears 11, 12 with the driven member 17, for braking the latter by connecting it with the member 22, or for permitting the driven member 17 to rotate freely with respect to the other driven member 4 and driven gears 11, 12.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic and specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. A driving arrangement for controlling the rotary movements of the working members of two-lap lapping or grinding machines comprising, in combination: a first driven member and a coaxial second driven member; a first and a second driven gear both coaxial with said driven members and each having an axial bore bounded by axially parallel groove means, said first gear rigidly connected with said first driven member; means ineluding a motor for rotating said gears in opposing directions; and an axially shiftable coupling member co-. axially connected with the second driven member and coaxially extendable through the bores of said gears, said coupling member comprising spline means alternately receivable in the grooves of said gears whereby the first gear is drivingly connected with the second driven member when its bore receives said spline means and the coupling member drivingly connects the second gear with said second driven member when its spline means enters the bore of said second gear, the coupling members having a neutral axial position in which it is discona nected from said gears.

2. A driving arrangement for controlling the rotary movements of the Working members of two-lap lapping or grinding machines comprising, in combination: a first drive-n member and a coaxial second driven member; a

first and a second driven gear both coaxial with said driven members and each having an axial bore bounded by axially parallel groove means, said first gear rigidly connected with said first driven member; means including a motor for rotating said gears in opposing directions; a stationary braking member having a bore coaxial with the bores of said gears and bounded by axially parallel groove means; and an axially shiftable coupling member coaxially connected with the second driven member and coaxially extendable through the bores of said braking member and said gears, said coupling member comprising spline means alternately receivable in the grooves of said gears and of said braking member whereby the first gear is drivingly connected with the second driven member when its bore receives said spline means and the coupling member drivingly connects the second gear with said second driven member when its spline means enters the bore of said second gear, the coupling member having a neutral axial position in which it is disconnected from said gears and from said braking member, and a fourth axial position in which spline means enters the bore of said braking member whereby the second driven member is held against rotary movements by said braking member.

3. A driving arrangement for controlling the rotary movements of the working members of two-lap lapping or grinding machines comprising, in combination: a first driven member and a coaxial second driven member; a first and a second driven gear both coaxial with said driven members and each having an axial bore bounded by axially parallel groove means, said first gear rigidly connected with said first driven member; means for rotating said gears in opposite directions and comprising a motor, a shaft axially parallel With said driven gears, means drivingly connecting the motor with said shaft, a first driving gear member coaxially fixed on said shaft and meshing with said first driven gear, a second driving gear member fixed on said shaft, and an intermediate gear member meshing with said second driving gear member and with said second driven gear for rotating the second driven gear in a direction counter to the direction of rotation of said second driving gear member; and an axially shiftable coupling member coaxially connected with the second driven member and coaxially extendable through the bores of said gears, said coupling member comprising spline means alternately receivable in the grooves of said gears whereby the first gear is drivingly connected with the second driven member when its bore receives said spline means and the coupling member drivingly connects the second gear with said second driven member when its spline means enters the bore of said second gear, the coupling member having a neutral axial position in which it is disconnected from said gears.

4. A driving arrangement for controlling the rotary movements of the Working members of two-lap lapping or grinding machines comprising, in combination: a first driven member and a coaxial second driven member; a first and a second driven 'gear both coaxial with said driven members and each having an axial bore bounded by axially parallel groove means, said first gear rigidly connected with said first driven member; means for rotating said gears in opposing directions and comprising a motor, a shaft axially parallel with said driven gears, a first pulley connected with and driven by said motor, a second pulley, an endless belt mounted on said pulleys for rotating the second pulley, a worm fixed to and driven by the second pulley, a Worm wheel fixed. on said shaft and meshing With said Worm for transmitting rotation of the second pulley to said shaft, a first driving gear member fixed on the shaft and meshing with the first driven gear, a second driving gear member fixed on the shaft, and an intermediate gear member meshing with said second driving gear member and with said second driven gear for rotating the latter in a direction counter to the directionof rotation ofsaid second driving gear member;

and an axially shiftable coupling member coaxially connected with the second driven member and coaxially e'xtendable through the bores of said gears, said coupling member comprising spline means alternately receivable in the grooves of said gears whereby the first gear is drivingly connected with the second driven member when its bore receives said spline means and the coupling member drivingly connects the second gear with said second driven member when its spline means enters the bore of said second gear, the coupling member having a neutral axial position in which it is disconnected from said gears.

5. A driving arrangement for controlling the rotary movements of the working members of two-lap lapping or grinding machines comprising, in combination: a first driven member and a coaxial second driven member, said second driven member having a coaxial bore formed with axially parallel grooves; a first and a second driven gear both coaxial with said driven members and each having an axial bore bounded by axially parallel groove means, said first gear rigidly connected with said first driven member; means including a motor for rotating said gears in opposing directions; and an axially shiftable coupling member, said coupling member having splines permanently received and axially shiftable in the bore of said second driven member whereby said splines and said grooves constitute a driving connection between the second driven member and said coupling member, said coupling member coaxially extendable through the bores of said gears, and comprising spline means alternately receivable in the grooves of said gears whereby the first gear is drivingly connected with the second driven memher when its bore receives said spline means and the coupling member drivingly connects the second gear with said second driven member when its spline means enters the bore of said second gear, the coupling member having a neutral axial position in which it is disconnected from said gears.

.6. A driving arrangement for controlling the rotary movements of the working members of two-lap lapping or grinding machines comprising, in combination: a first driven member and a second driven member; a first and a'second driven gear both coaxial with said second driven member and each thereof having an axial bore and a clutch member, said first gear drivingly connected with the first driven member; means including a motor for rotating said gears in opposing directions; and an axially shiftable coupling member coaxially connected with and axially shiftable relative to said second driven member, said coupling member coaxially extendable into the bores of said gears and having a clutch member alternately engageable with the clutch members of said gears whereby the first gear is drivingly connected with the second i driven member when its clutch member engages with the clutch member of said coupling member and said coupling drivingly connects the second gear with said second driven member when its clutch member engages with the clutch member of said second gear, said coupling member having a neutral position in which its clutch member is disconnected from the clutch members of said gears.

7. A driving arrangement for controlling the rotary movements of the working members of two-lap lapping or grinding machines comprising, in combination: a first driven member and a second driven member; a first and a second driven gear both coaxial with said second driven member and each thereof having an axial bore and a clutch member, said first gear drivingly connected with the first driven member; means including a motor for rotating said gears in opposing directions; stationary braking means having a bore coaxial with the bores of said gears and a clutch member; and an axially shiftable coupling member coaxially connected with and axially shiftable relative to said second driven member, said coupling member coaxially extendable into the bores of said gears and having a first and a second clutch member with said first clutch member alternately engageable with the clutch members of said gears whereby the first gear is drivingly connected with the second driven member when its clutch member engages with the first clutch member of said coupling member and said coupling member drivingly connects the second gear with said seconddriven member when its first clutch member engages with' the clutch member of said second gear, said coupling member having a neutral position in which its first clutch member is disconnected from the clutch members of said gears and a fourth position in which its second clutch member engages with the clutch member of said braking means whereby the second driven member is held against rotary movements.

8. In a two lap lapping machine, in combination; a lower lap having a vertical shaft; an upper laphaving a vertical shaft; an endless belt drive for each of said shafts, each of said belt drives comprising a driving pulley, said pulleys coaxial with and vertically spaced from each other with the upper pulley drivingly connected to the shaft of the upper lap and the lower pulley drivingly connected to the shaft of the lower lap; and a driving arrangement for operating said laps comprising a first and a second gear both coaxial with and disposed between said pulleys, both said gears having coaxial bores formed with axially parallel groove means, said first gear closer to and drivingly fixed to said lower pulley; means including a single motor for rotating said gears in opposing directions; and a vertically reciprocable coupling member coaxial with said pulleys, having an upper end drivingly coupled to and axially shiftable with respect to said upper pulley, and comprising spline means alternately receivable in the bores of said gears for drivingly connecting the respective gear with said upper pulley, said coupling member having a neutral position in which it is disconnected from said gears whereby the upper pulley is free to rotate relative to said gears.

9. In a two-lap lapping machine, in combination: a lower frame comprising a vertical center support having an axial bore formed with axially parallel grooves; an upper frame rotatably mounted on said center support; a lower lap having a vertical shaft rotatably mounted in said lower frame; an upper lap having a vertical shaft rotatably mounted in said upper frame; a first endless belt drive in said lower frame drivingly connected with the shaft of said lower lap and comprising a lower driving pulley coaxial with said center support; a second endless belt drive in said upper frame drivingly connected with the shaft of said upper lap and comprising an upper driving pulley coaxial with said lower pulley; and a driving arrangement for operating said laps comprising an upper and a lower gear mounted in the lower frame coaxially with said pulleys, said lower gear drivingly connected with the lower pulley for rotating the lower lap, each of said gears having a coaxial bore formed with axially parallel grooves; means including a motor in the lower frame drivingly connected with the gears for rotating the same in opposing directions; and a vertically reciprocable coupling member coaxial with and axially shiftably connected for rotation with said upper pulley, said coupling member having a first annularly arranged group of splines alternately receivable in the bores of said gears for drivingly connecting the respective gear with the upper pulley, and a second annularly arranged group of splines spaced from said first group in such a manner 'as tobe receivable in the bore of said center support when the coupling member is disconnected from said gears whereby the center support holds the upper pulley against rotary movements, and said coupling member having a neutral position in which its splines are disengaged from said gears and from said center support whereby the upper pulley is free to rotate with the upper lap relative to said gears.

10. In a two-lap lapping machine, in combination, a lower lap having a vertical shaft; an upper lap having a vertical shaft; and endless belt drive for each of said shafts, each of said belt drives comprising a driving pulley, said driving pulleys coaxial with and vertically spaced from each other with the upper pulley drivingly connected to the shaft of the upper lap and the lower pulley drivingly connected to the shaft of the lower lap; and a driving arrangement for operating said laps comprising a first and a second driven gear both coaxial with and disposed between said pulleys, each driven gear having an axial bore and a clutch member, said first driven gear drivingly connected to said lower pulley, means including a motor for rotating said driven gears in opposing directions, and an axially shiftable coupling member co axially connected with and axially shiftable relative to said upper pulley, said coupling member coaxially extendable into the bores of said driven gears and having a clutch member alternately engageable with the clutch members of said driven gears whereby the first driven gear is drivingly connected with the upper pulley when its clutch member engages with the clutch member of said coupling member and said coupling member drivingly connects the second driven gear with said upper pulley when its clutch member engages with the clutch member of said second driven gear, said coupling member having a neutral position in which its clutch member is disconnected 'from the clutch members of said driven gears.

11. In a two-lap lapping machine, in combination, a lower lap having a vertical shaft; an upper lap having a vertical shaft; an endless belt drive for each of said shafts, each of said belt drives comprising a driving pulley, said driving pulleys coaxial with and vertically spaced from each other with the upper pulley drivingly connected to the shaft of the upper lap and the lower pulley drivingly connected to the shaft of the lower lap; stationary braking means having a bore coaxial with said driving pulleys and a clutch member; and a driving arrangement for operating said laps comprising a first and a second driven gear both coaxial with and disposed between said pulleys, each driven gear having an axial bore and a clutch member, said first driven gear drivingly connected to said lower pulle means including a motor for rotating said driven gears in opposing directions, and an axially shiftable coupling member coaxially connected with and axially shiftable relative to said upper pulley, said coupling member coaxially extendable into the bores of said driven gears and having a first and a second clutch member with said first clutch member alternately engageable with the clutch members of said driven gears whereby the first driven gear is drivingly connected with the upper pulley when its clutch member engages with the first clutch member of said coupling member and said coupling member drivingly connects the second driven gear with said upper pulley when its first clutch member engages with the clutch member of said second driven gear, said coupling member having a neutral position in which its first clutch member is disconnected from the clutch members of said driven gears, and a fourth position in which its second clutch member engages with the clutch member of said braking means whereby the upper driving 0 pulley is held against rotary movements.

No references cited. 

